| Interface | Description |
|---|---|
| ContentHandlerFactory |
This interface defines a factory for content handlers.
|
| CookiePolicy |
CookiePolicy implementations decide which cookies should be accepted
and which should be rejected.
|
| CookieStore |
A CookieStore object represents a storage for cookie.
|
| DatagramSocketImplFactory |
This interface defines a factory for datagram socket implementations.
|
| FileNameMap |
A simple interface which provides a mechanism to map
between a file name and a MIME type string.
|
| ProtocolFamily |
Represents a family of communication protocols.
|
| SocketImplFactory |
This interface defines a factory for socket implementations.
|
| SocketOption<T> |
A socket option associated with a socket.
|
| SocketOptions |
Interface of methods to get/set socket options.
|
| URLStreamHandlerFactory |
This interface defines a factory for
URL stream
protocol handlers. |
| Class | Description |
|---|---|
| Authenticator |
The class Authenticator represents an object that knows how to obtain
authentication for a network connection.
|
| CacheRequest |
Represents channels for storing resources in the
ResponseCache.
|
| CacheResponse |
Represent channels for retrieving resources from the
ResponseCache.
|
| ContentHandler |
The abstract class
ContentHandler is the superclass
of all classes that read an Object from a
URLConnection. |
| CookieHandler |
A CookieHandler object provides a callback mechanism to hook up a
HTTP state management policy implementation into the HTTP protocol
handler.
|
| CookieManager |
CookieManager provides a concrete implementation of
CookieHandler,
which separates the storage of cookies from the policy surrounding accepting
and rejecting cookies. |
| DatagramPacket |
This class represents a datagram packet.
|
| DatagramSocket |
This class represents a socket for sending and receiving datagram packets.
|
| DatagramSocketImpl |
Abstract datagram and multicast socket implementation base class.
|
| HttpCookie |
An HttpCookie object represents an http cookie, which carries state
information between server and user agent.
|
| HttpURLConnection |
A URLConnection with support for HTTP-specific features.
|
| IDN |
Provides methods to convert internationalized domain names (IDNs) between
a normal Unicode representation and an ASCII Compatible Encoding (ACE) representation.
|
| Inet4Address |
This class represents an Internet Protocol version 4 (IPv4) address.
|
| Inet6Address |
This class represents an Internet Protocol version 6 (IPv6) address.
|
| InetAddress |
This class represents an Internet Protocol (IP) address.
|
| InetSocketAddress |
This class implements an IP Socket Address (IP address + port number)
It can also be a pair (hostname + port number), in which case an attempt
will be made to resolve the hostname.
|
| InterfaceAddress |
This class represents a Network Interface address.
|
| JarURLConnection |
A URL Connection to a Java ARchive (JAR) file or an entry in a JAR
file.
|
| MulticastSocket |
The multicast datagram socket class is useful for sending
and receiving IP multicast packets.
|
| NetPermission |
This class is for various network permissions.
|
| NetworkInterface |
This class represents a Network Interface made up of a name,
and a list of IP addresses assigned to this interface.
|
| PasswordAuthentication |
The class PasswordAuthentication is a data holder that is used by
Authenticator.
|
| Proxy |
This class represents a proxy setting, typically a type (http, socks) and
a socket address.
|
| ProxySelector |
Selects the proxy server to use, if any, when connecting to the
network resource referenced by a URL.
|
| ResponseCache |
Represents implementations of URLConnection caches.
|
| SecureCacheResponse |
Represents a cache response originally retrieved through secure
means, such as TLS.
|
| ServerSocket |
This class implements server sockets.
|
| Socket |
This class implements client sockets (also called just
"sockets").
|
| SocketAddress |
This class represents a Socket Address with no protocol attachment.
|
| SocketImpl |
The abstract class
SocketImpl is a common superclass
of all classes that actually implement sockets. |
| SocketPermission |
This class represents access to a network via sockets.
|
| StandardSocketOptions |
Defines the standard socket options.
|
| URI |
Represents a Uniform Resource Identifier (URI) reference.
|
| URL |
Class
URL represents a Uniform Resource
Locator, a pointer to a "resource" on the World
Wide Web. |
| URLClassLoader |
This class loader is used to load classes and resources from a search
path of URLs referring to both JAR files and directories.
|
| URLConnection |
The abstract class
URLConnection is the superclass
of all classes that represent a communications link between the
application and a URL. |
| URLDecoder |
Utility class for HTML form decoding.
|
| URLEncoder |
Utility class for HTML form encoding.
|
| URLStreamHandler |
The abstract class
URLStreamHandler is the common
superclass for all stream protocol handlers. |
| Enum | Description |
|---|---|
| Authenticator.RequestorType |
The type of the entity requesting authentication.
|
| Proxy.Type |
Represents the proxy type.
|
| StandardProtocolFamily |
Defines the standard families of communication protocols.
|
| Exception | Description |
|---|---|
| BindException |
Signals that an error occurred while attempting to bind a
socket to a local address and port.
|
| ConnectException |
Signals that an error occurred while attempting to connect a
socket to a remote address and port.
|
| HttpRetryException |
Thrown to indicate that a HTTP request needs to be retried
but cannot be retried automatically, due to streaming mode
being enabled.
|
| MalformedURLException |
Thrown to indicate that a malformed URL has occurred.
|
| NoRouteToHostException |
Signals that an error occurred while attempting to connect a
socket to a remote address and port.
|
| PortUnreachableException |
Signals that an ICMP Port Unreachable message has been
received on a connected datagram.
|
| ProtocolException |
Thrown to indicate that there is an error in the underlying
protocol, such as a TCP error.
|
| SocketException |
Thrown to indicate that there is an error creating or accessing a Socket.
|
| SocketTimeoutException |
Signals that a timeout has occurred on a socket read or accept.
|
| UnknownHostException |
Thrown to indicate that the IP address of a host could not be determined.
|
| UnknownServiceException |
Thrown to indicate that an unknown service exception has
occurred.
|
| URISyntaxException |
Checked exception thrown to indicate that a string could not be parsed as a
URI reference.
|
The java.net package can be roughly divided in two sections:
A Low Level API, which deals with the following abstractions:
Addresses, which are networking identifiers, like IP addresses.
Sockets, which are basic bidirectional data communication mechanisms.
Interfaces, which describe network interfaces.
A High Level API, which deals with the following abstractions:
URIs, which represent Universal Resource Identifiers.
URLs, which represent Universal Resource Locators.
Connections, which represents connections to the resource pointed to by URLs.
Addresses are used throughout the java.net APIs as either host identifiers, or socket endpoint identifiers.
The InetAddress class is the abstraction representing an IP (Internet Protocol) address. It has two subclasses:
Inet4Address for IPv4 addresses.Inet6Address for IPv6 addresses.But, in most cases, there is no need to deal directly with the subclasses, as the InetAddress abstraction should cover most of the needed functionality.
Not all systems have support for the IPv6 protocol, and while the Java networking stack will attempt to detect it and use it transparently when available, it is also possible to disable its use with a system property. In the case where IPv6 is not available, or explicitly disabled, Inet6Address are not valid arguments for most networking operations any more. While methods like InetAddress.getByName(java.lang.String) are guaranteed not to return an Inet6Address when looking up host names, it is possible, by passing literals, to create such an object. In which case, most methods, when called with an Inet6Address will throw an Exception.
Sockets are means to establish a communication link between machines over the network. The java.net package provides 4 kinds of Sockets:
Socket is a TCP client API, and will typically be used to connect to a remote host.ServerSocket is a TCP server API, and will typically accept connections from client sockets.DatagramSocket is a UDP endpoint API and is used to send and receive datagram packets.MulticastSocket is a subclass of DatagramSocket used when dealing with multicast groups.Sending and receiving with TCP sockets is done through InputStreams and OutputStreams which can be obtained via the Socket.getInputStream() and Socket.getOutputStream() methods.
The NetworkInterface class provides APIs to browse and query all the networking interfaces (e.g. ethernet connection or PPP endpoint) of the local machine. It is through that class that you can check if any of the local interfaces is configured to support IPv6.
A number of classes in the java.net package do provide for a much higher level of abstraction and allow for easy access to resources on the network. The classes are:
URI is the class representing a Universal Resource Identifier, as specified in RFC 2396. As the name indicates, this is just an Identifier and doesn't provide directly the means to access the resource.URL is the class representing a Universal Resource Locator, which is both an older concept for URIs and a means to access the resources.URLConnection is created from a URL and is the communication link used to access the resource pointed by the URL. This abstract class will delegate most of the work to the underlying protocol handlers like http or ftp.HttpURLConnection is a subclass of URLConnection and provides some additional functionalities specific to the HTTP protocol.The recommended usage is to use URI to identify resources, then convert it into a URL when it is time to access the resource. From that URL, you can either get the URLConnection for fine control, or get directly the InputStream.
Here is an example:
URI uri = new URI("http://java.sun.com/");
URL url = uri.toURL();
InputStream in = url.openStream();
myproto://myhost.mydomain/resource/), a similar URL will try to instantiate the handler for the specified protocol; if it doesn't exist an exception will be thrown.
By default the protocol handlers are loaded dynamically from the default location. It is, however, possible to add to the search path by setting the java.protocol.handler.pkgs system property. For instance if it is set to myapp.protocols, then the URL code will try, in the case of http, first to load myapp.protocols.http.Handler, then, if this fails, http.Handler from the default location.
Note that the Handler class has to be a subclass of the abstract class URLStreamHandler.
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For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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